WO2009110074A1

WO2009110074A1 - Process for producing plasma display panel and process for producing magnesium oxide crystal powder

Info

Publication number: WO2009110074A1
Application number: PCT/JP2008/053975
Authority: WO
Inventors: 智也三澤; 小坂　忠義; 瀬尾　欣穂
Original assignee: 株式会社日立製作所
Priority date: 2008-03-05
Filing date: 2008-03-05
Publication date: 2009-09-11
Also published as: JPWO2009110074A1; KR101106830B1; CN101919019B; JP4961495B2; US20110018169A1; KR20100090724A; CN101919019A

Abstract

A process for producing a plasma display panel (PDP) provided with a priming particle releasing layer containing a magnesium oxide crystal simultaneously exerting aggregation and discharge delay remedying effects. In particular, there is provided a process for producing PDP having, arranged so as to be exposed to discharge space, a priming particle releasing layer containing a magnesium oxide crystal having undergone high-temperature heating treatment, wherein in the step of heat treatment of magnesium oxide crystal powder as a raw material, the configuration and size of particle mass of magnesium oxide crystal powder are uniformized before the high-temperature heating treatment.

Description

Method for manufacturing plasma display panel, method for manufacturing magnesium oxide crystal powder

The present invention relates to a plasma display panel (PDP) and a manufacturing method thereof, and more particularly to a magnesium oxide crystal powder contained in a priming particle emission layer (electron emission layer) and a technique effective when applied to the manufacturing method. is there.

The resolution of PDP is increasing, and the address operation time for selecting and deciding lighting / non-lighting of the display cell increases as the number of pixels increases. In order to suppress this increase, it is effective to reduce the pulse width of the address discharge voltage (address voltage). However, there is a variation in the time (discharge delay) from when a voltage is applied to when discharge occurs. Therefore, if the pulse width of the address voltage is too small, no discharge may occur even when a pulse is applied. In that case, the display cell does not light correctly during the sustain period, resulting in image quality degradation.

As a means for improving the discharge delay of the PDP, as described in JP-A-2006-59786 (Patent Document 1), so as to be exposed to a discharge space between two opposing substrate structures, There is a technique of providing a magnesium oxide crystal layer as a priming particle emission layer (electron emission layer).
JP 2006-59786 A

According to Japanese Patent Application No. 2007-124718, which was a previous application by the present inventors, as a means for obtaining a higher discharge delay improvement effect in the above-described magnesium oxide crystal layer, a halogen element was mixed in the magnesium oxide crystal powder. And there is a technique of firing. Further, according to PCT / JP2007 / 68348, which is a previous application filed by the present inventors, there is a technique for heat-treating magnesium oxide crystal powder in an oxidizing atmosphere.

However, there are cases where aggregates are present in the magnesium oxide crystal powder heat-treated by these techniques. If a large agglomerate is present in the priming particle emitting layer in the PDP, the spread of discharge may be hindered to cause display defects, or display unevenness may occur due to variations in characteristics between cells.

As a method for eliminating the agglomerates, a method of pulverizing the magnesium oxide crystal powder after the heat treatment with a mortar and a pestle, or performing a dispersion treatment such as ultrasonic waves on the slurry during wet application to the panel There are methods. However, these methods sometimes destroy the magnesium oxide crystals and impair the discharge delay improvement effect.

The present invention has been made in view of the problems as described above, and its purpose is to provide a technique that makes it possible to achieve both the suppression of aggregation of the heat-treated magnesium oxide crystal powder and the effect of improving the discharge delay. There is to do.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows. That is, the PDP manufacturing method according to the exemplary embodiment of the present invention manufactures a PDP in which a priming particle emitting layer including magnesium oxide crystal powder that has been heat-treated at high temperature is disposed so as to be exposed to the discharge space. The method is characterized in that a high-temperature heat treatment is performed after a pretreatment step for making the shape and size of the particle group of the raw material magnesium oxide crystal powder uniform.

Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows. That is, according to a typical embodiment of the present invention, since contact between particle groups during high-temperature heating is reduced, a magnesium oxide crystal powder in which aggregation is suppressed without impairing the effect of improving discharge delay is obtained. be able to. By disposing the priming particle emitting layer containing the magnesium oxide crystal powder, it is possible to realize a PDP that achieves both improvement in discharge delay and suppression of display defects and display unevenness.

It is the figure which showed the outline | summary about the example of the pre-processing process which makes the shape and size of a particle group uniform in Embodiment 1 of this invention. It is the figure which showed the manufacturing flow of the magnesium oxide crystalline substance powder and the priming particle | grain release layer including the pre-processing process in Embodiment 1 of this invention. It is the figure which showed the outline | summary about the example of the pre-processing process which makes the shape and size of the particle group uniform in Embodiment 2 of this invention. (A), (b) is the figure which showed the example of the state of the fusion | melting at the time of heating a particle | grain (particle group) at high temperature. It is the figure which expanded and showed the example of the basic structure of PDP which is one embodiment of this invention as an exploded perspective structure. It is the figure which showed the example of the cross-sectional structure of the front substrate structure containing the priming particle | grain discharge | release layer in PDP of one embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

<Overview>
In the method for producing a PDP according to an embodiment of the present invention, in the priming particle emitting layer, in order to realize both the suppression of aggregation of the heat-treated magnesium oxide crystal and the effect of improving the discharge delay, which are the problems described above, In the heat treatment step of the magnesium oxide crystal powder, before the heat treatment, the shape and size of the particle group of the raw material magnesium oxide crystal powder are made uniform so that the particle groups can be in contact with each other during the high-temperature heat treatment. Reduce.

Here, aggregation of particles or particle groups occurs when particles (particle groups) in contact with each other at high temperature heating are fused together. FIG. 4 is a diagram showing an example of a fusion state when particles (particle groups) are subjected to high-temperature heat treatment. As shown in FIG. 4A, when the shape and size of the particles (particle group) 40 are not uniform during high temperature heating, the contact between the particles (particle group) 40 is increased, and the fusion 41 after high temperature heating is performed. Since the area of the substrate becomes larger, the aggregation becomes stronger. On the other hand, as shown in FIG. 4B, when the shape and size of the particles (particle groups) 40 are uniform, the contact between the particles (particle groups) 40 can be minimized, and after high-temperature heating. The area of the fusion 41 is reduced and aggregation is weakened.

Therefore, before the high-temperature heat treatment of the magnesium oxide crystal powder, if the shape and size of the particles (particle groups) are not uniform, make them uniform to reduce contact between the particles (particle groups). Thus, aggregation due to fusion of particles (particle groups) during high-temperature heat treatment is suppressed. By using the magnesium oxide crystal powder in which aggregation is suppressed for the priming particle emitting layer, it is possible to realize a PDP that achieves both improvement in discharge delay and suppression of display defects and display unevenness.

<PDP (basic structure)>
FIG. 5 is a diagram showing an example of a basic structure of a PDP (panel) 1 according to an embodiment of the present invention. FIG. 5 shows a set of display cells (Cr, Cg, Cb) corresponding to pixels. For the sake of explanation, the x direction (first direction, horizontal direction), y direction (second direction, vertical direction), and z direction (third direction, panel surface vertical direction) are shown.

The PDP 1 is formed by combining the front substrate structure 10 and the rear substrate structure 20 and has a discharge space 26 therebetween. In the front substrate structure 10, a group of display electrodes 12 (12X, 12Y) is arranged on the front glass substrate 11 in the x direction. The display electrode 12 includes a sustain electrode 12X for a sustain operation and a scan electrode 12Y for a sustain operation and a scan operation (shared). The display electrode 12 (12X, 12Y) is composed of, for example, a transparent electrode and a bus electrode. On the front glass substrate 11, the display electrode 12 group is covered with a dielectric layer 13. A protective layer 14 is further formed on the dielectric layer 13. The dielectric layer 13 and the protective layer 14 are formed on the entire surface corresponding to the display area (screen) of the PDP 1.

In the back substrate structure 20, a group of address electrodes 22 is arranged on the back glass substrate 21 in the y direction intersecting with the display electrodes 12. The group of address electrodes 22 is covered with a dielectric layer 23. A partition wall 24 is formed at a position corresponding to between the address electrodes 22 on the dielectric layer 23, for example, in the y direction. The barrier ribs 24 divide the discharge space 26 corresponding to the unit light emitting areas (display cells). In the region partitioned by the partition wall 24 above the address electrode 22 (z direction), phosphors (phosphor layers) 25 (25r, 25g, R) of each color of R (red), G (green), and B (blue) 25b) are formed by color-coding in order for each region (column).

The internal region formed by bonding the front substrate structure 10 and the back substrate structure 20 is sealed with a discharge gas (for example, a gas in which Ne is mixed with several percent of Xe), thereby being airtight. The discharge space 26 is configured. The peripheral part of PDP1 is bonded together with a sealing material. A display cell is configured corresponding to the intersection of the sustain electrode 12X, the scan electrode 12Y, and the address electrode 22.

In the driving of the PDP 1 (subfield method and address display separation method), a discharge (address discharge) is generated by applying a voltage between the address electrode 22 and the scan electrode 12Y in the selected display cell (address operation period). In addition, a discharge (sustain discharge (display discharge) or the like) is generated between the pair of display electrodes 12 (12X, 12Y) with respect to the selected display cell (sustain discharge (display discharge)) (sustain operation period). Thus, light emission (lighting) is performed in a desired display cell in the subfield. In addition, the luminance of the pixel (display cell) is expressed by selecting a subfield to be lit in the field.

<PDP (detailed structure)>
FIG. 6 is a diagram illustrating an example of a cross-sectional configuration of the front substrate structure 10 including the priming particle emitting layer in the PDP 1 according to the embodiment of the present invention. The front substrate structure 10 of the PDP 1 has a priming particle emitting layer 15 formed on the surface of the protective layer 14 so as to be exposed to the discharge space 26. The priming particle release layer 15 is a magnesium oxide crystal layer containing magnesium oxide (MgO) crystal powder. Alternatively, the priming particle emitting layer 15 includes a magnesium oxide crystal powder to which a halogen element such as fluorine (F) is added. In the priming particle emitting layer 15, the magnesium oxide crystal powder is densely or sparsely distributed with respect to the target surface (protective layer 14) (the sparsely distributed layer is also called a layer (film)).

A transparent material such as glass can be used for the front glass substrate 11. The display electrode 12 can be composed of, for example, a transparent electrode 12a having a wide width formed of ITO (indium tin oxide) or the like and a bus electrode 12b having a narrow width made of a metal such as Cu or Cr and reducing the electrode resistance. . The electrode shape is not particularly limited. For example, the transparent electrode 12a has a plate shape or a T shape for each display cell, and the bus electrode 12b has a linear shape.

The display electrode 12 forms a display line by a pair of the adjacent sustain electrode 12X and the scan electrode 12Y. As an electrode arrangement configuration, a normal configuration in which a pair of display electrodes 12 serving as non-discharge regions (reverse slits) is provided, or display electrodes 12 (12X, 12Y) are alternately arranged at equal intervals, and all adjacent display electrodes 12 are arranged. A so-called ALIS (Alternate Lighting Surfaces Method) configuration in which a display line is configured by a pair of the above is possible.

The dielectric layer 13 is formed, for example, by applying a low melting point glass paste on the front glass substrate 11 by screen printing or the like and baking it. The protective layer 14 has functions such as protecting the dielectric layer 13 and emitting secondary electrons. The protective layer 14 is made of, for example, a metal oxide such as magnesium oxide, calcium oxide, strontium oxide, or barium oxide, and is preferably made of a magnesium oxide layer having a high secondary electron emission coefficient. The protective layer 14 is formed by, for example, an electron beam evaporation method (or a sputtering method, a coating method, etc.).

The back substrate structure 20 can be manufactured using a known technique as follows, for example. The rear glass substrate 21, the address electrode 22, the dielectric layer 23, and the like can be manufactured in the same manner as the front substrate structure 10. The partition wall 24 can be, for example, a stripe shape only in the y direction, or a box shape having partition walls in the x direction and the y direction. The phosphor 25 is formed for each of R, G, and B, for example, by applying a phosphor paste to a region between the barrier ribs 24 by a method such as a screen printing method or a dispenser and baking it.

<Priming particle release layer (magnesium oxide crystal layer)>
The priming particle emitting layer (magnesium oxide crystal layer) 15 is disposed at any location exposed to the discharge space 26 in the substrate structure constituting the PDP 1. For example, a configuration directly disposed on the dielectric layer 13 or a configuration disposed on the protective layer 14 on the dielectric layer 13 is possible. In the present embodiment, as shown in FIG. 6, the front substrate structure 10 is arranged on the protective layer 14. By adopting a configuration in which the priming particle emission layer 15 is disposed so as to be exposed to the discharge space 26, the priming particles are emitted to the discharge space 26 by the priming particle emission layer 15 (magnesium oxide crystal powder constituting the same). The function and the effect of improving the discharge delay in the PDP 1 can be obtained.

The priming particle emitting layer 15 has a priming particle emitting powder material. The priming particle emitting powder material is made of magnesium oxide crystal powder (powder) or magnesium oxide crystal powder to which a halogen element is added.

The kind of halogen element to be added is, for example, one or more of fluorine (F), chlorine, bromine, iodine and the like. In the case of using fluorine, it has been confirmed that the effect of improving the discharge delay lasts for a long time. The amount of halogen element added is, for example, 1 to 10,000 ppm. Examples of the halogen-containing material include magnesium fluoride (MgF ₂ ), which is a halide of magnesium, and halides of Al, Li, Mn, Zn, Ca, and Ce.

Calcination of the substance containing magnesium oxide crystal powder is performed within a range of 1000 to 1700 ° C., for example. The particle size after heat treatment of the magnesium oxide crystal powder or the magnesium oxide crystal powder to which a halogen element is added is preferably within a predetermined range (50 nm to 20 μm). If the particle size is too small, the effect of improving the discharge delay by the priming particle emitting layer 15 is small. On the other hand, if the particle size is too large, the priming particle releasing layer 15 is difficult to be formed uniformly.

The basic formation method of the priming particle emitting layer 15 is, for example, as follows. A paste or slurry (priming particle emitting powder-containing material) prepared by mixing magnesium oxide crystal powder with a solvent (solvent) is prepared. This material is deposited on the target surface by a method such as spraying (spreading) or coating. For example, a slurry spraying method or a paste spraying method by a printing method can be used. Moreover, the priming particle emitting layer 15 is completed by removing the solvent component or the like by drying or baking the deposited material and fixing the powder component to the target surface. For example, the priming particle emitting layer 15 is formed to have a predetermined thickness over the entire target surface (the surface of the protective layer 14).

<Embodiment 1>
Below, the manufacturing method of PDP1 which has the priming particle | grain discharge | release layer 15 containing the magnesium oxide crystal powder which is Embodiment 1 of this invention and this magnesium oxide crystal powder is demonstrated. The manufacturing method of PDP 1 of the present embodiment includes a pretreatment step for making the shape and size of the particle groups uniform before heat-treating the raw material powder of the magnesium oxide crystal powder at a high temperature.

FIG. 1 is a diagram showing an outline of an example of a pretreatment process for making the shape and size of the particle group uniform in the present embodiment, and FIG. 2 is an oxidation including the pretreatment process in the present embodiment. FIG. 5 is a diagram showing a manufacturing flow of a magnesium crystal powder and a priming particle release layer 15.

In FIG. 2, in the present embodiment, as the raw material powder 103 before the high-temperature heat treatment (step S2), a magnesium oxide (MgO) crystal powder 201 is added to a flux (a substance that lowers the melting point of magnesium oxide). (Flux)) 202 is added with magnesium fluoride (MgF ₂ ) which is a halide of magnesium.

Here, the magnesium oxide crystal powder 201 is manufactured by Ube Materials Co., Ltd., trade name: high-purity ultrafine powder magnesia (2000A), and flux 202 is manufactured by Furuuchi Chemical Co., Ltd., magnesium fluoride. (MgF ₂ ) (purity 99.99%) is used, and these are mixed so that the molar ratio is MgO: MgF ₂ = 1: 0.0001. The state of the raw material powder 103 may be a slurry mixed with a volatile solvent or a mixture of a binder in addition to a dry powder.

For example, the raw powder 103 is processed as shown in FIG. 1 as a pretreatment step (step S1) for making the shape and size of the particle group uniform. In FIG. 1, first, a substrate 101 having a plurality of concave holes 102 on the surface is prepared. The size (width and depth of the opening) of the concave hole 102 is 1 μm to 100 μm, although it depends on the particle size distribution of the powder after heat treatment, the design of the upper limit of allowable aggregation, the heat treatment conditions, the size of the display cell, etc. It is desirable.

The material of the substrate 101 is not particularly limited, but metal, glass, resin, or the like can be used. In the present embodiment, it is assumed that a concave hole 102 having an opening width of 50 μm and a depth of 25 μm is formed on the surface of a flat substrate 101 made of glass by a sandblast method. The substrate 101 may be other than a flat plate, such as a roll. Moreover, although the shape of the concave hole 102 is illustrated as a hemispherical shape in FIG. 1, it is not particularly limited to this.

The raw material powder 103 is filled in the concave hole 102 on the substrate 101 by using a squeegee 104 or the like. Thereafter, by turning the substrate 101 upside down and applying vibrations or the like, a particle group 105 made of the raw material powder 103 that is uniformly shaped into the shape and size of the concave hole 102 is obtained.

Next, the obtained particle group 105 is collected in a high-temperature heating tray, and a high-temperature heat treatment (step S2) in FIG. 2 is performed. When slurry and a binder are mixed with the raw material powder 103, a drying process is performed before collection | recovery. Further, in order to minimize contact between the particle groups 105, care is taken not to apply vibration, pressure, or the like to the obtained particle group 105 from after collection until high-temperature heat treatment. In this embodiment, the obtained particle group 105 is heat-treated at 1450 ° C. for 4 hours in an atmosphere of nitrogen (N): oxygen (O) = 4: 1 as an oxidizing atmosphere.

The heat-treated magnesium oxide crystal powder 203 is mixed at a rate of 2 g (2 g / L) with respect to 1 L of IPA (isopropyl alcohol) as the solvent 204 (step S3) to obtain a slurry 205.

The slurry 205 is sprayed on the surface (target surface) of the front substrate structure 10 on which the protective layer 14 (magnesium oxide layer) in FIG. The layer (film) is formed by spraying or coating. And the said priming particle | grain discharge | release layer 15 is completed by drying the said layer (slurry 205) by heating (solvent component removal etc.) (process S4). In addition, the amount of formation (application) of the slurry 205 is set to 2 g / m ² .

5 is manufactured using the front substrate structure 10 on which the priming particle emitting layer 15 is formed by the above-described process.

As described above, in the step of producing the priming particle emitting layer 15, the shape and size of the particle group 105 made of the magnesium oxide crystal powder 201 are made uniform by including the pretreatment step (step S1). By reducing the contact between the particle groups 105 during the high-temperature heat treatment (step S2), the magnesium oxide crystal powder 203 in which aggregation is suppressed can be obtained without impairing the effect of improving the discharge delay. . By disposing the priming particle emitting layer 15 including the magnesium oxide crystal powder 203, it is possible to realize a PDP 1 that achieves both improvement in discharge delay and suppression of display defects and display unevenness.

<Embodiment 2>
The manufacturing method of PDP 1 having the magnesium oxide crystal powder according to the second embodiment of the present invention and the priming particle releasing layer 15 including the magnesium oxide crystal powder is the same as the magnesium oxide crystal shown in FIG. In the production flow of the body powder 203 and the priming particle release layer 15, another means is used in the pretreatment step (step S1) for making the shape and size of the particle group of the raw material powder 103 uniform. The processing contents of other steps are the same as those in the first embodiment.

FIG. 3 is a diagram showing an outline of an example of a pretreatment step (step S1) for making the shape and size of the particle group uniform in the present embodiment. First, a substrate 101 having a plurality of through holes 106 on the surface is prepared. The size of the through-hole 106 (the width of the opening and the thickness of the substrate) depends on the particle size distribution of the heat-treated powder, the design of the upper limit of allowable aggregation, the heat treatment conditions, the size of the display cell, etc., but 1 μm to 100 μm It is desirable that

The material of the substrate 101 is not particularly limited, but metal, glass, resin, or the like can be used. The substrate 101 may have a plate shape or a shape in which a wire or the like is knitted. In this embodiment, it is assumed that the substrate 101 is knitted with a SUS wire so that the width of the opening is 50 μm. In addition, although the shape of the through-hole 106 is illustrated as a cylindrical shape in FIG. 3, it is not particularly limited thereto.

The raw material powder 103 is pushed into the through hole 106 of the substrate 101 with a constant pressure using a squeegee 104 or the like, and is passed through the through hole 106. As a result, the shape and size of the particle group 105 made of the raw material powder 103 that has passed through the through-hole 106 become uniform. The raw material powder 103 is the same as that in Embodiment 1. Similarly to the first embodiment, the state of the raw material powder 103 may be a slurry mixed with a volatile solvent or a mixture of a binder in addition to a dry powder.

As described above, as in the first embodiment, in the step of producing the priming particle emitting layer 15, the pretreatment step (step S1) includes the particle group 105 made of the magnesium oxide crystal powder 201. Magnesium oxide crystals that can be made uniform in shape and size and have reduced aggregation without impairing the effect of improving discharge delay by reducing the contact between the particle groups 105 during the high-temperature heat treatment (step S2) Powder 203 can be obtained. By disposing the priming particle emitting layer 15 including the magnesium oxide crystal powder 203, it is possible to realize a PDP 1 that achieves both improvement in discharge delay and suppression of display defects and display unevenness.

As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

The present invention can be used for a PDP and a manufacturing method thereof.

Claims

A method of manufacturing a plasma display panel in which a priming particle emitting layer including a magnesium oxide crystal powder subjected to high-temperature heat treatment is disposed so as to be exposed to a discharge space between two opposing substrate structures,
Before the magnesium oxide crystal powder is subjected to the high-temperature heat treatment, it has a pretreatment step for making the shape and size of a particle group composed of a plurality of particles of the magnesium oxide crystal powder uniform. A method for manufacturing a plasma display panel.
In the manufacturing method of the plasma display panel of Claim 1,
In the pretreatment step, the shape and size of a particle group composed of a plurality of particles of the magnesium oxide crystal powder are formed by filling and molding the magnesium oxide crystal powder in a concave hole provided on the substrate. A method of manufacturing a plasma display panel, characterized in that the plasma display panel is uniform.
In the manufacturing method of the plasma display panel of Claim 2,
A method of manufacturing a plasma display panel, wherein the size of the concave hole is 1 to 100 μm.
In the manufacturing method of the plasma display panel of Claim 1,
In the pretreatment step, the magnesium oxide crystal powder is pushed and passed through a through-hole provided on the substrate, so that the shape and size of the particle group composed of a plurality of particles of the magnesium oxide crystal powder are uniform. A method of manufacturing a plasma display panel, characterized by comprising:
In the manufacturing method of the plasma display panel of Claim 4,
A method of manufacturing a plasma display panel, wherein the size of the through hole is 1 to 100 μm.
A method of manufacturing a plasma display panel in which a priming particle emitting layer including a magnesium oxide crystal powder subjected to high-temperature heat treatment is disposed so as to be exposed to a discharge space between two opposing substrate structures,
When the magnesium oxide crystal powder is subjected to the high-temperature heat treatment, the magnesium oxide crystal powder particles or particles having a uniform shape and size are used. A method for manufacturing a plasma display panel.
In a plasma display panel, a high-temperature heat-treated magnesium oxide crystal powder contained in a priming particle emitting layer disposed so as to be exposed to a discharge space between two opposing substrate structures. And
Before the magnesium oxide crystal powder is subjected to the high-temperature heat treatment, it has a pretreatment step for making the shape and size of a particle group composed of a plurality of particles of the magnesium oxide crystal powder uniform. Method for producing magnesium oxide crystal powder.
In the manufacturing method of the magnesium oxide crystal powder according to claim 7,
In the pretreatment step, the shape and size of a particle group composed of a plurality of particles of the magnesium oxide crystal powder are formed by filling and molding the magnesium oxide crystal powder in a concave hole provided on the substrate. A method for producing a magnesium oxide crystal powder characterized by making it uniform.
In the manufacturing method of the magnesium oxide crystal powder according to claim 8,
A method for producing a magnesium oxide crystal powder, wherein the size of the concave hole is 1 to 100 μm.
In the manufacturing method of the magnesium oxide crystal powder according to claim 7,
In the pretreatment step, the magnesium oxide crystal powder is pushed and passed through a through-hole provided on the substrate, so that the shape and size of the particle group composed of a plurality of particles of the magnesium oxide crystal powder are uniform. A method for producing a magnesium oxide crystal powder characterized by comprising:
In the manufacturing method of the magnesium oxide crystal powder according to claim 10,
A method for producing a magnesium oxide crystal powder, wherein the size of the through hole is 1 to 100 μm.